Gather 80,000 people together anywhere in the world, and it’s not surprising when tempers flare. On the evening of Sept. 23, riots broke out among workers employed by Foxconn, the world’s largest electronic-parts maker, forcing assembly lines in the northern Chinese city of Taiyuan to sit idle for a day. Thousands of people were involved in the melee, which was sparked by security guards’ assault of a Foxconn worker who failed to show his identification upon entering a dormitory, according to information supplied by factory employees to two NGOs that monitor labor conditions in China. Pictures and video posted online showed broken windows and a Foxconn shuttle bus with a damaged window, although it is difficult to confirm the authenticity of the images.

Meanwhile, China’s state-run Xinhua news agency reported that the brawl stemmed from fighting at a Foxconn dormitory between employees from two Chinese provinces, Shandong and Henan, prompting 5,000 security forces to swarm the scene. Foxconn Technology Group released a statement on Monday that about 40 people had been taken to the hospital with injuries after a “personal dispute between several employees escalated into an incident involving some 2,000 workers.” The company’s statement continued, “The cause of this dispute is under investigation … but it appears not to have been work-related.”

Foxconn, which is Taiwan-owned, employs about 1 million people across China. Its customers include a Who’s Who of leading electronics firms, from Apple and Microsoft to Nokia and Sony. The Taiyuan plant, where insiders say components for the iPhone 5 were assembled this summer, began operations eight years ago. Today it employs more than 79,000 people in a sooty provincial capital once better known for its coal mines and steel mills. Earlier this year, workers staged a short strike over salary; last October, the local government urged Foxconn to stop emitting noxious fumes that were disturbing locals living near the factory.

What exactly caused the Sept. 23 Taiyuan riot is still unclear. In June, a riot near a Foxconn plant in the southwestern Chinese city of Chengdu was initially linked to labor issues. But it turned out that an unrelated dispute between Foxconn workers and a restaurant owner had triggered the unrest. Still, Foxconn has been criticized in the past for the working conditions at its factories, especially after a string of worker suicides two years ago. Last year, four Foxconn workers in Chengdu were killed when a buildup of aluminum dust exploded in an inadequately ventilated workshop where Apple products were made. After consumer pressure mounted, Apple signed off on an audit by the Fair Labor Association, which found that more than half the surveyed workers in Chengdu had either seen or been involved in an accident.

Last week, to coincide with the release of the new iPhone 5, the Hong Kong–based NGO Students and Scholars Against Corporate Misbehavior published a report on Foxconn, accusing the partsmaker of subjecting workers to excessive overtime and low wages despite vows by Foxconn and Apple to improve labor conditions, noting, “When the peak season comes, [workers] are tied to the production lines with just one day off in 13 working days, or no rest day at all in a month, all to cope with the public demand for the new Apple products.”

When I was working on a story about Apple in China earlier this year, Louis Woo, a special assistant to Foxconn CEO Terry Gou, told me, “Since we are the largest consumer-electronics maker in the world and probably the largest private employer in China, this position carries a certain social responsibility. Foxconn is not perfect — there is no such thing as a perfect factory — but we aspire to be a better company every day.” It’s true that Foxconn’s profile has ballooned because of its relationship with the world’s most valuable company, Apple. If the Taiyuan riot had occurred at a domestic manufacturer of Chinese electronics, the world’s attention wouldn’t have been trained on a coal town few non-Chinese could identify. But that’s the price of success for Foxconn and Apple.